Stephanollona serrata (Osburn, 1912),
treatment provided by
|Stephanollona serrata (Osburn, 1912)|
( Fig. 38View FIGURE 38; Table 37)
Hippothoa biaperta: Smitt 1873: 46 (part), pl. 8, fig. 174?
Lepralia serrata Osburn, 1912: 242 , pl. 26, fig. 57 a-c.
Hippoporina contracta: Osburn 1940: 428 (part?); Maturo 1968: 52 (part?). Cleidochasma contractum: Cheetham & Sandberg 1964: 1032 , text-fig. 38; Winston 1982: 148, fig. 81. Stephanollona serrata: Winston 2005: 115 , figs 321–326.
Material examined. VMNH. no. 70659; USNM. no. 128262.
Description. Colony encrusting ( Fig. 38View FIGURE 38 A), unilaminar to multilaminar. Zooids oval to polygonal; frontal shield surface uneven with smooth microstructure and indistinct zooidal boundaries, marginal areolar pores obvious ( Fig. 38View FIGURE 38 B, C). Orifice with distinct narrow rim; bases of articulated hollow spines 4 around distal part of rim ( Fig. 38View FIGURE 38 D); anter evenly rounded, with beaded margin, a pair of bean-shaped condyles with concave edges, and broadly U-shaped sinus. Avicularia oval to spatulate, with complete crossbars and rostra with serrated edges, oriented in various directions and raised at angle to frontal surface ( Fig. 38View FIGURE 38 B). Ooecia hyperstomial, broader than long, with heavily calcified ectooecium, semicircular tabula exposing entooecium, very short broad labellum with lateral indentations, and narrow transverse opening not closed by the zooid operculum ( Fig. 38View FIGURE 38 C).
Remarks. Like ‘ Cleidochasma porcellanum ’, ‘ Cleidochasma contractum ’ also represents a widely distributed species complex, now recognized on the basis of orificial beading and ooecial characters to be related to Phidoloporidae rather than Cleidochasmatidae . Its species are currently placed in the genus Stephanollona (Gordon 1994; Cook & Bock 1996).
Distribution. Cape Hatteras to Florida, Caribbean, Gulf of Mexico.
Material examined. Holotype: VMNH no. 70660.
Etymology. Genitive plural of the Latin diminutive, conchula, of small snails, alluding to the species’ habit of encrusting snail shells.
Diagnosis. Stephanollona species occurring on small snail shells, characterized by 5 orificial spines, small oval frontal avicularia angled on a large projection, and a narrow, shallowly concave sinus.
Description. Small colonies encrusting calcareous substrata, primarily microgastropod shells ( Fig. 39View FIGURE 39 A). Zooids rounded, hexagonal; frontal shield imperforate except for marginal pores, surface having smooth knobbly texture, proximal surface low, distal surface raised surrounding orifice ( Fig. 39View FIGURE 39 B). Orifice bordered by smooth raised rim, with 5 hollow distal spines ( Fig. 39View FIGURE 39 D, E); anter subcircular with with beaded rim, narrow flattened scalloped condyles, and narrow shallowly concave sinus. Laterofrontal avicularium oval, with complete crossbar and slightly serrated rostrum present on some zooids, raised at angle on large projection subjacent to sinus. Ooecia prominent, ectooecium enveloped in frontal calcification, proximofrontally bearing semicircular tabula exposing entooecium; labellum very broad and narrow with lateral indentations; ooecial opening well above primary orifice. ( Fig. 39View FIGURE 39 C, E).
Remarks. The species is very similar to both Stephanollona serrata (above) and six-spined Stephanollona asper also found on the Floridan Atlantic coast. It differs from Stephanollona asper in having only five oral spines, and from S. serrata in having a broader sinus and avicularia that vary in position. In addition to the differences in spine number, S. asper has more elaborate cross bars on avicularia, large spatulate avicularia, and a different orifice. Stephanollona serrata has more positionally varied avicularia, and a broader sinus.
Distribution. East coast of Florida, Oculina banks.
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